MEXICAN President Felipe Calderon headed to his country’s most violent city yesterday after deadly attacks on US consular staff and their families upped the ante in his battle against drug gangs.

Gunmen stormed a Guatemalan prison and gunned down four jailed police officers in a mafia hit, the country’s leader said.

An agent for the US FBI said today that a grenade found near the podium in the Georgian capital where US President George Bush gave a speech last week had been thrown and was live but apparently failed to explode due to a malfunction.